Dual batteries

[Ridowh 8]

I recently needed to replace the battery on my 2015 GTS. It had always been a pain, losing charge if left too long, however now I’m living back in the U.K. (from Australia), where it is significantly colder and darker at this time of year, I saved my pennies and put in the Superbatt SB072 80Ah recommended in the thread on here. This has a good deal more capacity than the old one and so far is working without fault. 

What I would like to know is has anyone fitted two batteries in their 86?

My reason for asking is that I require a CPAP machine to sleep at night due to some breathing problems and severe obstructive apnoea. I am hoping to travel around the U.K. this summer on a photographic tour of all the places I would have loved to have seen before I got married, and emigrated 25 years ago. I never had the car or the money at the time.  Then I ended up married and on the other side of the world (I have heard of murderers, back in old days, that got less than me). Anyway, not being able to afford accommodation, I intend to sleep in the car when I can, and I have a 12v DC->230v AC inverter on order. Ideally I would be able to use the old battery to power my CPAP at night and recharge it while driving during the day. I should be able to secure it into the boot area and wire it up (in parallel) such that I can switch it to charge each morning and take it out of the car’s circuitry at night. 

What I wondered was if my 2015 GTS86 will happily charge the two batteries in parallel? Or would I be overloading the alternator / charging circuits?

[TommyC 33]

I think this is quite a technical question with many variables that you’ll need to know/find out.

First you need to know how much energy your apnoea machine uses. It must have a wattage rating somewhere on it? You’ll need to know how much the inverter can deliver as it might not be up to the job?! 🤔😬

How long do you need to use it for on an average night?

With the right inverter you can cook a roast dinner in your home oven from 12v, but you’d probably need a few thousand amps!!

For example: your upgraded battery is rated at 80Ah (Amp-hours). So it can deliver 80 amps for an hour-ish (this won’t really do it any good mind you!). Conversely it can deliver 1 amp for 80 hours-ish.

With the wattage of your apnoea machine you’ll need to convert this to amps...

E.g. 1000watts / 12volts = 83.333 amps

10watts / 12volts = 0.8333amps

(this calculator/converter will help, plus the explanations are fairly good if you scroll down 🙂 https://www.inchcalculator.com/watts-to-amps-calculator/  ).

Once you know how many amps the machine will draw you’ll know if the battery will be up to the job! (It might only last half the night and need a full recharge, which will be too much for the alternator to cope with 😔 but on the other hand it might only draw a few amps over the whole night and you might be fine 😊 ).

 

Your idea is still possible at a high-ish current draw though...

It could be that you’ll need a leisure battery and charger, like those for caravans, to power the machine for a few days. Then maybe schedule some stops at caravan sites and use the hook-up electricity to re-charge as and when needed 🙂

Or if you could build it all into a little luggage-like trolley you could treat yourself to a cheap hotel/B&B every few days. A proper bed for the night and recharge the battery while you’re at it 😀

Whilst touring the country on motorbikes I’ve paid as little as £20 for a nice hotel room for the night!! 😀

[Andrew Smith 156]

I would say that you need a leisure battery and split charger as found in camper vans for this, easy enough to install as I have done it in my own van. A regular car starter battery would soon discharge

[Ridowh 8]

Tommy and Andrew - thank you so much for all the info. I will need to look into getting the info required when I get time. Then I’ll look into whether or not it’s something I’m able to do. 

Even though electronics (engineering) is a long-standing hobby of mine, there are still limits to what I am comfortable doing with a car, especially given the complexity of electrics in modern cars and motorcycles. I normally shy away from anything too risky, seeing as my 86 is the first car I’ve ever bought outright and, just as when I had motorcycle, I’m hesitant to risk anything that may result in a cascade failure, which would typically occur when I am driving somewhat enthusiastically. 

I’ll see how I get on. 

Very much appreciated. 

 

Richard 

[Toybaru1 15]

Why not get a small jump pack , Halfords etc. Charge it during the day from the power socket and us that during the night?

[Church 209]

My choice would be single battery with total charge (and probably weight) similar to planned two combined.

Jump pack .. in my eyes there is drawback, that if it is going to be needed several times, that is main battery had ran flat several times. Batteries don't like to run completely empty, that happening repeatedly may mean they'll degrade / reduce max charge / life.

[Varelco 211]

Hi Septic,

It's definitely doable, If it was me I'd tuck a deep cycle (aka Leisure) battery into the corner of the boot with some sort of bracketry to hold it in situ and install a split charging setup. I don't know what you power demands will be but I can't imagine you will need a large battery.

You will want it configured so that the leisure battery and car battery can be isolated from each other for 2 situations;

1. Engine starting, this absorbs a huge amount of current, Leisure batteries do not have a high enough current rating to start a car engine.

2. Overnight use, to minimise the risk of draining both the leisure battery and car battery.

Although if I'm honest, is it really worth the effort? I've slept in a car a few times and its not a pleasurable experience. Its either extremely cold or extremely hot, you build up massive amounts on condensation (will be even worse in the small cabin of an 86) and their is literally no sound insulation or blocking out light. So its earplugs and something over your eyes. Not to mention the fact you are confined to one position in a seat. You can get an Air BnB room for not alot of money. The money you spend rigging up this dual battery setup will cover you for a few nights using Air BnB.

 

 

[Andrew Smith 156]

To go the leisure battery route you would need the battery, 110mha is good and a split charger system  https://www.megavanmats.online/product-page/5m-mvm-split-charge-relay-kit-ready-made The split charger is a relay that allows the leisure battery to be charged from the starter battery only when it sees a certain voltage ie when the engine is running, so it never drains your starter battery. Its quite easy to install... bolt in leisure battery to  run +ve from starter batt to relay with in line fuse, relay +ve to leisure batt with in line fuse. Earth leisure bat and relay and that's the charging side of it done. Afraid I don't know anything about inverters but you would need to find out if you could run one without fully discharging a leisure battery
 

[Ridowh 8]

2 hours ago, Toybaru1 said:

Why not get a small jump pack , Halfords etc. Charge it during the day from the power socket and us that during the night?

I have a very smart, very compact (smaller than a paperback novel) jump starter battery. It recharges via the 5v USB output in the car, or can be mains charged via an adapter. When I get the inverter I will test it out overnight and see whether it has the low current, continuous drain capacity (vs. the high current, short term power needed for a car start). 

And of course I also have my old, original Toyota battery that was replaced. 

The replacment is an 80Ah (vs. the original’s 45Ah). I am not certain how suitable that would be being used for up to 8 continuous hours. 

According to the manufacturer’s website for my sleep apnoea machine, for a 12v, deep cycle battery, using an inverter, it will draw 0.9 Amps. Given this, I should think that the old battery I have may well manage OK. However I will need to look into the complexities of wiring required to ensure that it is safely connected up to both the car and the inverter.

Perhaps even using just the car’s single existing 80Ah battery will be totally sufficient. Then I can keep the Lipo jump start unit ready in case of higher than expected drain. That would certainly keep costs and complexity low. 

[Ridowh 8]

1 hour ago, Varelco said:

Air BnB.

Hmm thanks Varelco. They didn’t exist the last time I had any kind of freedom of movement (i.e. before I got married). 

I will check out these. My budget is incredibly tight though. I am disabled and survive on £120 a week from ESA. Luckily I own my own flat and car outright, so no debts, but it makes trying to go anywhere for any kind of holiday just about impossible  I have window coverings from Aus - needed the keep the sun out - and a good (Artic rated) sleeping bag and pillows. I have to sleep slightly raised anyway to assist with breathing and my cervical spine requires me to stay fairly immobile while sleeping so space isn’t too much of a problem for me  I will definitely be carrying out a few trial runs before undertaking any major journeys or spending out any significant sums of money. 

[Ridowh 8]

31 minutes ago, Andrew Smith said:

110mha is good and a split charger syste

Andrew is this correct? Seems awfully low. 

[Church 209]

I had slept in car once. Verdict was - never again :/ (though as it was in winter, engine kept running). Awful feel in morning. Or i'do like friend did, that chose for his fishing & hunting trips big SUV, whose rear seats could be folded to form completely flat floor. But most probably just paying for room/hotel or sleeping in tent.

[Varelco 211]

57 minutes ago, Septic said:

Hmm thanks Varelco. They didn’t exist the last time I had any kind of freedom of movement (i.e. before I got married). 

I will check out these. My budget is incredibly tight though. I am disabled and survive on £120 a week from ESA. Luckily I own my own flat and car outright, so no debts, but it makes trying to go anywhere for any kind of holiday just about impossible  I have window coverings from Aus - needed the keep the sun out - and a good (Artic rated) sleeping bag and pillows. I have to sleep slightly raised anyway to assist with breathing and my cervical spine requires me to stay fairly immobile while sleeping so space isn’t too much of a problem for me  I will definitely be carrying out a few trial runs before undertaking any major journeys or spending out any significant sums of money. 

It's pretty good, you can head down from about £20+ per night, usually in somebodies spare room.  Assuming you got yourself a smartphone its worth having the app on there...

[Andrew Smith 156]

6 hours ago, Septic said:

Andrew is this correct? Seems awfully low. 

sorry I meant 110ah, I'll get my coat lol

[surrey86 352]

Theoretically while it may be possible I think your back would be f*cked after spending multiple nights in a GT86. Better off getting cheap hotels, youth hostels / airbnb. 

[TommyC 33]

I’ve spent a few nights in mine on the passenger seat, on some very cold nights too! Arctic sleeping bag kept me toasty warm and a comfortable angle of recline is achievable. It was my feet that weren’t happy come the mornings, I think they were a bit cramped!